Method and apparatus for making hollow rubber articles



J. F2. GAMMETER METHOD AND APPARATUS FOR MAKING HOLLOW RUBBER ARTICLES Filed Sept. 20. 1924. 3 sheets-s eet 1 Oct. 26 1926.

- LGMBM J. R. GAMMETER METHOD AND APPARATUS FOR MAKING HOLLOW RUBBER ARTICLES 3 Sheets-Sheet 2 Filed Sept. 20, 1924 27 Fla /3 7572 2 Oct. 26 1926 J. R. GAMMETER MLIHOD AND APPARATUS FOR MAKING HOLLOW RUBBER ARTICLES Filed se i. 20. 192

3 Sheets-Sheet 5 WHEY 77 5 I JAY/72'? fi-EEmme/E urrr;

sa'ra Prawn JOHN R. GAMMETER, 0F AKRON, OHIO. ABSIGNOR TO THE B. F. GOODRICE'. COMPANY, OF NEW YORK, N. Y., A CORPORATION 011" NEW YORK.

METHOD. APPARATUS FOR MAKING HOLLDW RUBBER ARTICLES.

Application filed September 20, 1924. Serial. No. $8,814.

This invention relates to the manufacture of hollow rubber articles and more particularly to a means of producing sound projectors such as are commonly used in radio reception.

An object of this invention is to provide an improved method of producing sound projectors from hard rubber and for removing the cores employed in the molding and curing operations. A further object is to provide an improved core construction for forming sound projectors, and also to provide an improved means for removing such core construction from the sound projector after vulcanization.

In the manufacture of hard rubber sound projectors, and similar hollow articles having relatively be desirable, if not essential to satisfactory products, when the articles are to be cured in open heat, to applg hea pressure to the walls of the uncure artic e during a preliminary molding or forming step, which necessitates a sturdy core for supporting the walls of the article during the performance of said step. The removal of cores of this character irom sound projectors of the usual conformation presents some difficulties by reason of the sinuous conformation of the neck portion. Ihave devised a core consisting of two detachable sections or mandrels, a bell-shaped mandrel for the flaring end of the projector of cast iron or other durable material and a hollow or tubular neck-forming mandrel of low fusing metal. The removal of this core-construction from the projector, after vuliaiiization, is thereby greatly facilitated. The bell shaped mandrel is easily slipped from the horn and the fusible mandrel, forming a relatively small portion of the entire core structure, is melted out, preferably by flushing into the pro- 'ector hot metal of thesame alloy as the fusible mandrel, or other liquid, such as oil, which is not miscible with the mandrel metal.

- In the accompanying drawing, Fig. 1 is a view in vertical section showing an early stage in the formation of a soun pI'0]eCi0I, the core, the unvulcaiiized stock th reon, and the mold being represented in position for the moldin operation; Fig. 2 is a view in elevation illustrating the molded projector upon the core and supported for curing in thin walls, I have found it to' dry heat; Fig. 3 is a cross-section on the line of Fig. 1; Fi t is a view partially in section and partial y in elevation illustrating a method of melting out the soft metal mandrel, Fig. 5 is a view in vertical section oi a modified form of the core construction illustrated in Fig. 1; Fig. 6 is a detailed front elevation, partly in section, of the fusible metal sectional core employed in my improved core construction, and Fig. 7 is a similar view or the sheet metal liner of Fig. 5.

eferring more particularly to the draw.- mg, 1. show in 1 a core for a sound projector consisting of a bell-shaped man drel 10 of cast iron or other material, and a hollow neck-forming mandrel 11 of fusible metal. lhis metal may be an alloy of lead and tin melting at about 850 {1, but any other suitable alloy of low melting temperature may be used. The mandrel 11 is tubular in form and open at both ends. It is provided at its inner end with a tapered flange 12 adapted to its within a com lemental recess 13 of the bell-shaped man rel 10. The flanged end of the fusible mandrel is interiorly formed with a shoulder 1a to provide an anchorage for a suitable means for securiiig'the two maiidrels together. As shown a bar 15 is pivotally secured to one end of a rod 16, the other end or the rod,

which is threaded and provided with a thumb nut 17, passes through a bar 18 the latter being secured to the outer end oi the bell-shaped mandrel 10. The arrangement is such that the two mandrels may be secure- 1y drawn together by anchoring the bar 15 against the shoulder 14 of the fusible mandrel and turning the thumb nut 17 into engagement with the bar 18. The unvulcan-- ized rubber stock is designated by the numeral 20 and is shown in'Fig. l placed about the maiidrels 10 and 11 and encased b the mold sections 21, one section only being s own in this figure.

hot fluid thercthrough.

of the fusible mandrel ll rests in a. groove at the top of the stand 26. After vulcanization, the bell shaped hiandrel is detached from the fusible mandrel 11, as by loosening the thumb nut 17 and disengaging the bar from the shoulder 14, and is withdrawn from the projector. Only the relatively small fusible mandrel 11 re mains still in the projector and this is removed quickly auo readily without straining or damagingthe projector by flushing a In order to facilitate the flow of the flushing metal through thebell, when metal is used, and to p 'cclude its adhesion thereto, 1 preferably paint the interior of the hell with mica. In practice,

. the projector is placed in a cradle which sound aves passing therethrough. manufacture of sound-promoters or the conforms in shape to the projector and enables it to be readily ant freely handled during the melting out process Without dis:

tortion of the projector or danger to the operator.

While it is to be understood that difl'erent ways of procedure may be followed in melting out the fusible mandrel, l have found a satisfactory method to conslst'in supporting the projector in the position shown in Fig. 4, pouring tour or five ladies full of hot metal of the same alloy as the fusible mandrel into the larger end of the projector and then gradually tilting it to the position indicated in thedotted lines indicated in Fig. t in order to draw or? both the this-bin; and the melted metal. In operation; upon projectors of small sizes, I have also found it to be desirable initially to pour some hot metal through the projector from the small end in order to enlarge the passage at the small end of the noel; and-thus to facilitate drainage upon flushing out the fusible n'iandrel in the manner above described. Other hot fluids may also be used inthe melting out operation, as for example high boiling oils or super-heated steam, a general desideratum being that these other. hot iluids shall not be miscible withlhe fused metal of the mandrel which for economical reasons should be saved for reuse.

In the modification shown in Fig. the neck forming" mandrel 31 is provided with a lbin sheet metal shell 32 which surrounds the fusible portion 83 of the mandrel ill.

The mandrels 3i and 34 are detachfably se- 1 cured together and the rubber stock fitted.

thereabout, "molded and vulcanized in the manner indicated hereinabove. In this case.

however, upon meltingout the fusible core the sheet metal shell is left Within the proiector to form a lining for the neck portion. This construction gives greater'strength to the neck of the projector and forms a smooth inner surface which minimizes distortions of In the leases e smaller sizes, the fusible portion 33 of the mandrel 31' may be omitted. In this case the which isegttremely cheap to manufacture,

particularly since the metal is used over and over again. The sheet metal shell 32, (Fig. 7) is likewise preferably made in two sections, for example by a stamping process, and the twohalves are secured to each other by crimping, soldering or other convenient means.

it is to be understood that the present invention contemplates broadly, the employment of a core composed of a readily fusible metal for the formation ofthe DQCllC portion oi the sound projcctiu' and the melting out or" the core alter the \llltzll'ilZflilOll thereof. lt further i'cnl'eiuplates' the employment of a fusible necleforming core either with or without the sheet metal shell or liner for reinforcing the neck of the projector. Furtberuuire, itis the intentiouof the present invention to cover all such modifications of the above described means as properly fall within the scope of the appended claims, and all analogous uses of the invention in melting hollow articles other than sound projeetors.

I. claim: a

1. The method of i'i'ianulacturing hollow vulcanized articles which comprises forming rulcanizablc rubber stock about a hollow fusible core open at both ends and which remains solid 'at tbetcmperaturcs of vulcanizatiom-rulcanizing the "formed rubber stock on the coreahd melting out the fusible core after vulcanization by passing through the stock on' the core at temperatures at which.

the core remains solid, and melting out the tumblecoreafter VlllCflDlZfltiODlW passing therethrmlgh in direct contact with the fusible metal otthe core a tluid of higher tempcralure'than the melting point of the core. 3. The method ol manufacturing sound rojcctors of hard rubber which comprises orming a core by detacbably securing to a bell-shaped mandrel a hollow neck-forming Hi l resents mandrel of low-fusing metal, co'verin'g the core with a vulcanizable rubh'erf stock, pressing the stock between said core and an ere tcrior mold to form the sound projector,

vulcanizing the formed rubber stock on the core, removing the bcll-shape'mandrel, and giellting out the hollow neck-forming man- 4:. The method of manufacturing sound projectors of hardrubbcr which comprises forming a core by detachably securing to a bell-shaped mandrel a hollow neck-forming mandrel of low-fusingmetal, covering the core with a vulcanizable rubber stock, pressing the stock between said core and an exteriormold to form the sound projector, vulcanizing the formed rubber stock on t e core, removing the bell-shape mandrel, and melting out the hollow neck-forming mandrel by pouring th'erethrough a fluid of higher temperature than the melting point of the fusible metal.

5. The method of manufacturing sound projectors of hard rubber which comprises forming a core by detachably securing to a bell-shaped mandrel a hollow neck-forming mandrel of a metal fusing at a temperature somewhat above the temperature of vulcanization employed, covering the core with a vulcanizable rubber stock, pressing the stock between said" core and an exterior mold to form the sound projector, removing the exterior mold, vulcanizing the formed rubber stock on the core, removing the bell-shape mandrel, and meltingout the hollow neckforming mandrel by pouring,- through the hollow core heated molten metal of the composition of the metal core.

6. The method of manufacturing sound projectors of hard rubber which comprises forming a coreby deteehably securing to a bell-shaped mandrel a hollow neck-forming mandrel of low-fusing metal having an extcrior sheet metal shell, covering the core with a vuleanizable rubber stock, pressing thestock between said core and an exterior mold to form the sound projector, removing the exterior mold, vulcanizing the formed ruhbcr stoclron the core, removing the bellshape mandrel and melting out the fusible metal of the neck-forming mandrel so as to entire core as can be readily removed int leave the sheet metal shell as a permanent lining for the neelz; of the sound projection 7. The method oi removing a, hollow core of low fusing metal from an article which comprises pouring through the hollow core in direct contact with the fusible mete;- of the core a fluid of higher temperature than the melting point or the fusible core,

8. The method of removing a. hollow core of low fusing metal "from a hard rubber ticle which comprises pouring through the core in direct contact vi ith the fusible metal of the core hot molten metal of the composition of the metal of the hollow core.

9. The method of removing from a vulcanized hard rubber article a hollow core of low fusing metal which comprises supporting the article against deformation, and pouring through the hollow, core in direct contact with the fusible metal of j e fluid of higher temperature than th incl 3 point of the fusible, core.

10. A core for the formation of hard. rubber sound projectors comprising a bell shaped mandrel forming such portion oithe from the vulcanized projector through 7 large open end thereof, and a fusible nest forming mandrel detachebly d thereto.

11. A core for the formation of hard rnbber sound projectors comp'risii'ig bell shaped mandrel and a hollow neck-forming mandrel of low-fusing metal detachabl sccured thereto.

12. A core for the formation of hard ruin her sound projectors comprising a bellshaped mandrel torming'snch portion. of the entire core as may be readily removed from the vulcanized projector through the large e open end thereof, and. a hollow, neclnformingmandrel of low-fusing metal, and means for detachably connecting said mandrels.

13. A core for the formation of hard rubher sound projectors includingva mandrel e1. fusible metal forming such portion of the entire core as cannot be readily relieved from the large open end of the projector.

In witness whereof I have hereunto set my hand this 18th day of September, 192%.

Jot-"tn n; dam/mania, 

